Azure IoT Device Telemetry Simulator

Master test and push

The IoT Telemetry Simulator allows you to test Azure IoT Hub, Event Hub or Kafka ingestion at scale. The implementation is communicating with Azure IoT Hub using multiplexed AMQP connections. An automation library allows you to run it as load test as part of a CI/CD pipeline.

A single AMQP connection can handle ~995 devices.

Quick start

The quickest way to generate telemetry is using docker with the following command:

docker run -it -e ";SharedAccessKeyName=device;SharedAccessKey=your-iothub-key" iottelemetrysimulator/azureiot-telemetrysimulator

The simulator expects the devices to already exist in Azure IoT Hub. If you need help creating simulation devices in an Azure IoT Hub use the included project IotSimulatorDeviceProvisioning or the docker image:

docker run -it -e ";SharedAccessKeyName=registryReadWrite;SharedAccessKey=your-iothub-key" -e DeviceCount=1000 iottelemetrysimulator/azureiot-simulatordeviceprovisioning

Simulator input parameters

The amount of devices, their names and telemetry generated can be customized using parameter. The list below contains the supported configuration parameters:

Name Description
IotHubConnectionString Iot Hub connection string. "Device" our "Iot Hub owner" scopes are good. Example:;SharedAccessKeyName=device;SharedAccessKey=your-iothub-key
EventHubConnectionString Event Hub connection string. SAS Policy "Send" is required. For EventHub no device registration is required. Example: Endpoint=sb://;SharedAccessKeyName=send;SharedAccessKey=your-send-sas-primary-key;EntityPath=your-eventhub-name.
KafkaConnectionProperties Kafka connection properties as a JSON string. Example: {"bootstrap.servers=kafka"}.
KafkaTopic Kafka topic name.
DeviceList comma separated list of device identifiers (default = ""). Use it to generate telemetry for specific devices instead of numeric generated identifiers. If the parameter has a value the following parameters are ignored: DevicePrefix, DeviceIndex and DeviceCount are ignored
DevicePrefix device identifier prefix (default = "sim")
DeviceIndex starting device number (default = 1)
DeviceCount amount of simulated devices (default = 1)
MessageCount amount of messages to send by device (default = 10). Set to zero if you wish to send messages until cancelled
Interval interval between each message in milliseconds (default = 1000)
Template telemetry payload template (see telemetry template)
FixPayload fix telemetry payload in base64 format. Use this setting if the content of the message does not need to change
FixPayloadSize fix telemetry payload size (in bytes). Use this setting if the content of the message does not need to change (will be an array filled with zeros)
PayloadDistribution Allows the generation of payloads based on a distribution
Example: "fixSize(10, 12) template(25, default) fix(65, aaaaBBBBBCCC)" generates 10% a fix payload of 10 bytes, 25% a template generated payload and 65% of the time a fix payload from values aaaaBBBBBCCC
Header telemetry header template (see telemetry template)
PartitionKey optional partition key template for Event Hubs (see telemetry template and Advanced options)
Variables telemetry variables (see telemetry template)
DuplicateEveryNEvents if > 0, send duplicates of the given fraction of messages. See Advanced options (default = 0)

Telemetry template

The simulator is able to create user customizable telemetry with dynamic variables (random, counter, time, unique identifier, value range).

To generate a custom telemetry it is required to set the template and, optionally, variables.

The template defines how the telemetry looks like, having placeholders for variables. Variables are declared in the telemetry as $.VariableName. The optional header defines properties that will be transmitted as message properties.

Variables are declared defining how values in the template will be resolved.

Built-in variables

The following variables are provided out of the box:

Name Description
DeviceId Outputs the device identifier
Guid A unique identifier value
Time Outputs the utc time in which the telemetry was generated in ISO 8601 format
LocalTime Outputs the local time in which the telemetry was generated in ISO 8601 format
Ticks Outputs the ticks in which the telemetry was generated
Epoch Outputs the time in which the telemetry was generated in epoch format (seconds)
MachineName Outputs the machine name where the generator is running (pod name if running in Kubernetes)

Customizable variables

Customizable variables can be created with the following properties:

Name Description
name Name of the property. Defines what will be replaced in the template telemetry $.Name
random Make the value random, limited by min and max
step If the value is not random, will be incremented each time by the value of step
min For random values defines it's minimum. Otherwise, will be the starting value
max The maximum value generated
values Defines an array of possible values. Example ["on", "off"]
customlengthstring Creates a random string of n bytes. Provide n as parameter

Example 1: Telemetry with temperature between 23 and 25 and a counter starting from 100


{ "deviceId": "$.DeviceId", "temp": $.Temp, "Ticks": $.Ticks, "Counter": $.Counter, "time": "$.Time" }


[{"name": "Temp", "random": true, "max": 25, "min": 23}, {"name":"Counter", "min":100}]


{ "deviceId": "sim000001", "temp": 23, "Ticks": 637097550115091350, "Counter": 100, "time": "2019-11-19T10:10:11.5091350Z" }
{ "deviceId": "sim000001", "temp": 23, "Ticks": 637097550115952079, "Counter": 101, "time": "2019-11-19T10:10:11.5952079Z" }
{ "deviceId": "sim000001", "temp": 24, "Ticks": 637097550116627320, "Counter": 102, "time": "2019-11-19T10:10:11.6627320Z" }

Running with docker:

docker run -it -e ";SharedAccessKeyName=device;SharedAccessKey=your-iothub-key" -e Template="{ \"deviceId\": \"$.DeviceId\", \"temp\": $.Temp, \"Ticks\": $.Ticks, \"Counter\": $.Counter, \"time\": \"$.Time\" }" -e Variables="[{name: \"Temp\", \"random\": true, \"max\": 25, \"min\": 23}, {\"name\":\"Counter\", \"min\":100} ]" iottelemetrysimulator/azureiot-telemetrysimulator

calling from PowerShell:

docker run -it -e ";SharedAccessKeyName=iothubowner;SharedAccessKey=your-iothub-key" -e Template="{ \"""deviceId\""": \"""$.DeviceId\""", \"""temp\""": $.Temp, \"""Ticks\""": $.Ticks, \"""Counter\""": $.Counter, \"""time\""": \"""$.Time\""", \"""engine\""": \"""$.Engine\""" }" -e Variables="[{name: \"""Temp\""", \"""random\""": true, \"""max\""": 25, \"""min\""": 23}, {\"""name\""":\"""Counter\""", \"""min\""":100}, {name:\"""Engine\""", values: [\"""on\""", \"""off\"""]}]" -e DeviceCount=1 -e MessageCount=3 iottelemetrysimulator/azureiot-telemetrysimulator

Example 2: Adding the engine status ("on" or "off") to the telemetry


{ "deviceId": "$.DeviceId", "temp": $.Temp, "Ticks": $.Ticks, "Counter": $.Counter, "time": "$.Time", "engine": "$.Engine" }


[{"name": "Temp", "random": true, "max": 25, "min": 23}, {"name":"Counter", "min":100}, {"name": "Engine", "values": ["on", "off"]}]


{ "deviceId": "sim000001", "temp": 23, "Ticks": 637097644549666920, "Counter": 100, "time": "2019-11-19T12:47:34.9666920Z", "engine": "off" }
{ "deviceId": "sim000001", "temp": 24, "Ticks": 637097644550326096, "Counter": 101, "time": "2019-11-19T12:47:35.0326096Z", "engine": "on" }

Running with docker:

docker run -it -e ";SharedAccessKeyName=device;SharedAccessKey=your-iothub-key" -e Template="{ \"deviceId\": \"$.DeviceId\", \"temp\": $.Temp, \"Ticks\": $.Ticks, \"Counter\": $.Counter, \"time\": \"$.Time\", \"engine\": \"$.Engine\" }" -e Variables="[{name: \"Temp\", \"random\": true, \"max\": 25, \"min\": 23}, {\"name\":\"Counter\", \"min\":100}, {name:\"Engine\", values: [\"on\", \"off\"]}]" iottelemetrysimulator/azureiot-telemetrysimulator

Generating high volume of telemetry

In order to generate a constant high volume of messages a single computer might not be enough. This section describes two way to run the simulator to ingest a high volume of messages

Azure Container Instance

Azure has container instances which allow the execution of containers with micro billing. This repository has a PowerShell script that creates azure container instances in your subscription. Requirements are having az cli installed.

To start the simulator in a single container instance:


You will be asked to enter the Azure IoT Hub Connection string. After that, a resource group and one or more container instances will be created.

The cloud runner can be customized with the following parameters (as -ParameterName ParameterValue):

Name Description
Location Location of the resource group being created. (Default = westeurope). For a list of locations try az account list-locations -o table
ResourceGroup Resource group (will be created if it does not exist) where container instances will be created. (Default = iothubsimulator)
DeviceCount Total amout of devices (Default = 100)
ContainerCount Total amount of container instances to create. The total DeviceCount will be divided among all instances (Default = 1)
MessageCount Total amount of messages to send per device. 0 means no limit, causing the container to never end. It is your job to stop and delete it! (Default = 100)
Interval Interval in which each device will send messages in milliseconds (Default = 1000)
Template Telemetry payload template to be used
(Default = '{ "deviceId": "$.DeviceId", "temp": $.Temp, "Ticks": $.Ticks, "Counter": $.Counter, "time": "$.Time", "engine": "$.Engine", "source": "$.MachineName" }')
PayloadDistribution Allows the generation of payloads based on a distribution
Example: "fixSize(10, 12) template(25, default) fix(65, aaaaBBBBBCCC)" generates 10% a fix payload of 10 bytes, 25% a template generated payload and 65% of the time a fix payload from values aaaaBBBBBCCC
Header Header properties template to be used
(Default = '')
Variables Variables used to create the telemetry
(Default = '[{name: "Temp", random: true, max: 25, min: 23}, {name:"Counter", min:100}, {name:"Engine", values: ["on", "off"]}]')
Cpu Amount of cpus allocated to each container instance (Default = 1.0)
IotHubConnectionString Azure Iot Hub connection string


This repository also contains a helm chart to deploy the simulator to a Kubernetes cluster. An example release with helm for 5000 devices in 5 pods:

helm install sims iot-telemetry-simulator\. --namespace iotsimulator --set iotHubConnectionString=";SharedAccessKeyName=iothubowner;SharedAccessKey=xxxxxxx" --set replicaCount=5 --set deviceCount=5000


The IotTelemtrySimulator.Automation .NET Core 2.1 library allows you to run the IoT Telemetry Simulator as part of a pipeline or any other automation framework. See the automation guide.

Advanced options

  • PartitionKey option for Event Hubs: When processing events downstream with a distributed engine, it is often more efficient to have related messages in the same partition. For example, if computing values over windows of events per device in Spark, having all the events for a given device in the same partition ensures they are received by a single compute node and ordered. On the other hand, the default round-robin behavior has advantages too, such as ensuring all partitions have equal load and that the system remains available even if a partition fails. Therefore, it is good to give the user control over the partition key.
  • DuplicateEvery option to duplicate events: Upstream systems generating events usually offer at-least-once delivery guarantees. Given that there is no mechanism in IoT Hub / Event Hubs for distributed transactions, it is always possible for the client not to receive the response from the server after sending a message, or crashing before persisting the response, and therefore to retry sending an event. This results in message duplicates. When testing event processing solution, it's important to inject such behavior so as to test if/how the system reacts to it, e.g. by deduplication. The option DuplicateEvery allows randomly duplicating a fraction of messages, e.g. setting DuplicateEvery to 1000 will duplicate messages with a probability of 1/1000 for each, i.e. will duplicate on average every 1000th message. Note that messages may be duplicated more than once: a message will be duplicated N times with a probability of 1/(DuplicateEvery)^N.